Fluid Diode Prosthetic Pulmonary Valve. Severe chronic pulmonary insufficiency is a known consequence of many congenital heart surgeries. Treatment by pulmonary valve replacement is often necessary when the individual reaches late adolescence or early adulthood. Little or no commercial development of pulmonary valve prostheses has occurred, but the number of young individuals that need pulmonary valve replacement has grown steadily through the years. The ideal pulmonary valve replacement should last indefinitely and have a low risk of thrombosis. Bioprosthetic valves do not currently have sufficient longevity to avoid reoperations for valve replacement if used in young or middle-aged adults. Mechanical valves are permanent, but unacceptably high rates of thrombosis have been documented, particularly for bileaflet designs, in the pulmonary position. The consequences include valve failure due to partial or total occlusion by leaflet malfunction. When used as pulmonary valves, mechanical valves are prone to abnormal diastolic leaflet movements, such as bouncing and failure to close, under normal pulmonic physiological conditions. Thrombogenicity of mechanical valve prostheses in the aortic and mitral positions has been linked to a combination of elevated stresses, zones of flow stasis, and materials. We present our clinical rationale, preliminary data, and design approach for a novel permanent prosthesis for the pulmonary position to regulate blood flow. The concept is based on fluid diode principles and it has no moving parts, yet it meets physiological performance needs based on preliminary results. Such a device also offers promise for complete manufacture using a low thrombogenic material, such as the successful diamond like coatings (DLC) or pyrolitic carbon biomaterial. Our aims are (1) to quantify the performance of valves based on this concept through in vitro fluid dynamic assessment and design tuning, and (2) to assess physiological compatibility and thrombotic potential of such valves through acute animal model studies. [unreadable] [unreadable] [unreadable]